I hear you and understand what you are saying, which is what makes this so frustrating. It is one or both bolts that are actually loosening up, and not the saddle shifting. The bolt was tight to begin with (to 7N-m as recommended) and the saddle was solid on the clamp with no shifting whatsoever. The shifting seems to begin after about 10-15 miles of riding (on paved roads - nothing unusual). The saddles used so far were a Brooks C13 with carbon rails and a Selle Anatomica with carbon rails. It happened with both. The back bolt has a washer that is beveled on one side so that it fits into a slightly countersunk opening on the little cylinder that extends through the back end of the post. There is no lock nut. The torx vs. hex thing is not the issue here but rather that the clamping mechanism will not keep the saddle secure. This will either resolve with loctite or I will sell it to somebody who likes these, put a Thomson back on, and move on. Too bad since it is a brand new post.